Andrea is performing two experiments to measure the correlation between sunlight exposure and fish activity. in one experiment, she uses a tank of goldfish in her home. she places the tank in the window on a sunny day and then on a cloudy day, each time recording the average amount of swimming done by the fish during several sample time intervals. in the second experiment, she observes the fish in the pond in her yard on two days, one sunny and one cloudy, and counts the number of times the fish surface looking for food during several time intervals.

which is a scientifically significant similarity between these experiments?
a) lack of controls
b) careful measurements
c) the use of domesticated fish
d) the same independent variable